Retrograde amnesia is the inability to retrieve information that was acquired before a particular date, usually the date of an accident or operation. There are two main types of amnesia: retrograde amnesia and anterograde amnesia.
The memory can be either wholly or partially lost due to the extent of damage that was caused. Amnesia is a deficit in memory caused by brain damage or disease, but it can also be caused temporarily by the use of various sedatives and hypnotic drugs.